Author // Sarah Buckley, M.D.
Perhaps the best-known birth hormone is oxytocin, the hormone of love, which is secreted during sexual activity, male and female orgasm, birth, and breastfeeding. Oxytocin engenders feelings of love and altruism; as Michel Odent says, “Whatever the facet of love we consider, oxytocin is involved.”
Oxytocin is made in the hypothalamus, deep inside the mammalian brain, and stored in the posterior section of the pituitary gland-the “master gland” of the endocrine (hormonal) system-which releases it in pulses. It is a crucial hormone in reproduction, and mediates what have been called the ejection reflexes: the sperm ejection reflex with male orgasm (and the corresponding sperm introjection reflex with female orgasm); the fetal ejection reflex at birth (a phrase coined by Odent for the powerful contractions at the end of an undisturbed labor, which birth the baby quickly and easily); and, postpartum, the placental ejection reflex, and the milk ejection or let-down reflex in breastfeeding.
As well as reaching peak levels in each of these situations, oxytocin is secreted in extra amounts during pregnancy, when it acts to enhance nutrient absorption, reduce stress, and conserve energy by making us more sleepy. Oxytocin also causes the rhythmic uterine contractions of labor; oxytocin levels peak at birth through stimulation of stretch receptors in a woman’s lower vagina as the baby descends.
High maternal oxytocin levels during labor and birth also benefit the baby. Research has found that maternal oxytocin crosses the placenta and enters the fetal brain during labor, when it acts to protect brain cells by switching them off, allowing low oxygen consumption at a time when fetal oxygen levels may be naturally low.
High maternal oxytocin levels continue after birth, culminating with the birth of the placenta, and are enhanced by the baby’s pre-breastfeeding and breastfeeding behaviors. Elevated maternal levels of oxytocin will protect against postpartum hemorrhage at this crucial time by ensuring efficient uterine contractions.
The baby also has been producing oxytocin during labor, perhaps even contributing to the processes of labor. So, in the minutes after birth, both mother and baby are bathed in an ecstatic cocktail of hormones. At this time, ongoing newborn oxytocin production is enhanced by skin-to-skin and eye-to-eye contact. Newborn levels begin to subside during the first hour after birth, but remain above normal for at least four days. Infant oxytocin levels are also elevated during and following breastfeeding, through activation of the vagal nerve.
During breastfeeding, oxytocin mediates the let-down reflex, and is released in pulses as the baby suckles. During the months and years of lactation, oxytocin continues to act to keep the mother relaxed and well-nourished. One researcher calls it “a very efficient anti-stress situation which prevents a lot of disease later on.” In her study, mothers who breastfed for more than seven weeks were calmer when their babies were 6 months old than mothers who did not breastfeed.
Outside of its role in reproduction, oxytocin is secreted in other situations of love and altruism (for example, when sharing a meal). Researchers have implicated malfunctions of the oxytocin system in conditions such as schizophrenia, autism, cardiovascular disease, and drug dependency, and have suggested that oxytocin may mediate the antidepressant effect of drugs such as Prozac. More recent research has implicated oxytocin in trusting interactions between individuals, which may reflect its role in lowering activity in the amygdala, a brain structure that processes fearful emotions.
This article appeared in Pathways to Family Wellness magazine, Issue #51.